1. Field of the Invention
The present invention relates to three-dimensional model generating systems and methods and computer programs therefor for extracting the three-dimensional shape of the ground on the basis of altitude information of the ground, which is obtained by an airplane, a satellite, or the like. In particular, the present invention relates to a three-dimensional model generating system and method and a computer program therefor for creating the appearance of a building having a three-dimensional shape on the basis of altitude information mapped onto a two-dimensional plane.
More particularly, the present invention relates to a three-dimensional model generating system and method and a computer program therefor for creating appearance information of individual buildings from altitude information mapped onto a two-dimensional plane and a building/road map. In particular, the present invention relates to a three-dimensional model generating system and method and a computer program therefor for generating building information in a more accurate manner regardless of the region in which the building is located.
2. Description of the Related Art
With the recent innovation of information technology, various types of information content are created and edited on computers to offer services such as information storage and information distribution. For example, map information indicating buildings and roads is integrated with geographic information on a computer to offer services that present regional information using map images for road guidance and tourist information. Also, real-time navigation services have been offered to mobile stations such as vehicles and ships using a user's current position information detected by GPS (Global Positioning System) or the like.
A map or geographic information is not only obtained by measurement on the ground, but also created on the basis of the results of observation from space by an airplane, a satellite, or the like. A recent airplane with a range sensor can compute the three-dimensional shape of the ground on the basis of measured altitude information of the ground. Maps, in general, are orthographic projections, whereas aerial photographs and satellite photographs are central projections. Altitude information measured from space is compensated for geographical errors, and the altitude information is made into an ortho-image on the basis of the accurate geographic information. As a result, the altitude information is mapped to each observation point on a map. In the description, “elevation-data” refers to data generated by mapping altitude information to each observation point on a two-dimensional plane.
Basically, map information is two-dimensional planar position information. The integration of the map information with such altitude information allows the relief of the ground to be represented. As a result, for example, a navigation system displays a stereoscopic three-dimensional map image by taking the relief of the ground and landscape into consideration. Such higher quality map information display services are thus offered. Alternatively, the three-dimensional map information is applied to public services such as flood control simulation or systems using virtual space.
Other applications of the altitude information include the creation of three-dimensional shape of a building. Specifically, a region in which a building is located (building-located region) is obtained from altitude information arranged on a two-dimensional plane and a separately prepared building map. The altitude is computed by smoothing the altitude information included in the building-located region. The altitude of the building-located region is raised by an amount equal to the computed altitude, thereby creating the three-dimensional shape of the building.
In such a case, a building such as a pyramid-shaped building having a shape that cannot be created by raising the bottom surface thereof experiences a problem in that a model having a different three-dimensional shape is created.